Journal of Applied Horticulture, 16(2): 141-145 2014
Studies on osmotic dehydration of banana cv. Poovan and Dwarf
Cavendish
T. Shanmugasundaram* and K. Haripriya
Department of Horticulture, Faculty of Agriculture, Annamalai University, Annamalainagar-608002, Tamil Nadu, India.
*E-mail: shaland4@yahoo.com
Abstract
The study was undertaken on osmotic dehydration of banana varieties viz., Poovan (AAB) and Dwarf Cavendish (AAA) to investigate
the effect of temperature, sample thickness and osmotic time on the rate of osmosis. The results revealed that the maximum water
loss and solid gain after osmosis were 57.9 and 15.5 per cent in Poovan and 53.1 and 11.8 per cent in Dwarf Cavendish. The moisture
content of Poovan slices reduced from 2.03 kg H2O kg-1 dry matter (DM) to as low as 0.31kg H2O kg-1 DM when osmosed in 60 ºB
syrup at 75 ºC. In case of Dwarf Cavendish, the moisture content reduced from 2.84 to 0.38 kg H2O kg-1 DM under similar conditions.
Subsequent air dehydration resulted in further loss of moisture and the moisture content was reduced to a range of 0.03 to 0.18 kg
H2O kg-1 DM after 4 to 8 h of drying.
Key words: Banana, post harvest loss, osmotic dehydration, value addition.
Introduction
Banana is one of the most important sustaining fruits in India
and its higher productivity demands good soil sturcture, nutrients
and water. The lands on which it can be successfully grown on
a commercial scale are therefore limited in extent. The banana
varieties grown on a commercial scale in Tamil Nadu are Poovan,
Dwarf Cavendish, Nendran, Red Banana, Robusta and Rasthali.
Among these varieties, Poovan is popularly consumed for relief
from constipation while Dwarf Cavendish assumes significance
due to its excellent flavour and taste.
The agro climatic conditions in India favour the cultivation
of wide variety of fruits. India is second largest producer of
fruits after after China with a production of 57.6 million tones
(MT) from 5.2 million ha (National Horticultural Board, 2005).
However, for various reasons this abundance of production is
not fully or satisfactorily utilized as it should be. About 25 to
35 per cent of this is wasted due to improper handling, lack of
transportation and storage facilities. To avoid the wastage, the
surplus fuir could be processed and preserved properly. Fruits
are generally preserved by canning, freezing, refrigeration or
by drying (Simmonds, 1966). Dehydration is one of the easiest
methods of preservation and is practiced from earliest times. A
dried fruit product, apart from increased shelf life, offers the
advantage of decreased weight and saves the cost of packaging,
handling and transporting the product.
Osmotic dehydration has received greater attention in recent
years as an effective method for preservation of several fruits
(Tiwari, 2005) and specially of banana (Gaspartero et al., 2003;
Chavan and Amarowicz, 2012). Osmotic dehydration is a twostage dehydration process. The first step consists of immersing
food piece in a concentrated osmotic solution or in a dry
osmotic material. To produce a stable dehydrated product, the
concentrated food may be vacuum dried or air dried in the second
stage (Contreras and Smyrl, 1981). The main principle involved
in osmotic dehydration is dewatering of fruits by osmosis at
comparatively lower temperature which reduces the severity of
the thermal treatment and produces dehydrated fruit product very
near to natural fruit in colour, flavour and textural qualities. The
sugar or syrup has a protective effect on the retention of fresh fruit
flavour during the process. Enzymatic and oxidative browning
reactions which normally occur during drying are prevented in
osmotic drying as the fruit pieces are surrounded by sugar, making
it possible to retain good colour (Chaudhari et al., 1993). With
growing importance of preservation, the present study was carried
on osmotic dehydration of banana varieties viz., Poovan (AAB)
and Dwarf Cavendish (AAA) and the effect of temperature,
sample thickness and osmotic time on the rate of osmosis.
Materials and methods
The study was carried out using two varieties of banana viz.,
Poovan (AAB) and Dwarf Cavendish (AAA). The variety Poovan
(AAB) was obtained from the Department of Horticulture,
Annamalai University, Annamalainagar and Dwarf Cavendish
was procured from farmer’s field. Fully matured fruits were
procured, washed in tap water to remove the extraneous matter
and shade dried. Damaged and bruised fruits were culled out. The
fruits were taken for peeling and sizing when the total soluble
solids (TSS) reached 17 to 22 oBrix for Poovan (AAB) and 22 to
25 oBrix for Dwarf Cavendish (AAA). Osmosis was carried out
on 5, 7.5 and 10 mm thickness of fruits in 40, 50 and 60 oBrix
concentration of sugar syrup maintaining a fruit to syrup ratio
of 1:4. Potassium metabisulphite and citric acid of 0.1 per cent
concentration each were added to the sugar syrup to enhance
the shelf life of dehydrated product. Observations on moisture
content, weight reduction and solid gain were recorded for every
2, 1 and 0.5 h dehydration at room temperature (RT), 50 and 75
o
C, respectively. Each treatment was repeated three times and
the average values were determined.
The observations were statistically anaylsed in factorial
142
Studies on osmotic dehydration of banana cv. Poovan and Dwarf Cavendish
completely randomized design in (FCRD) to study the influence
of osmosis time, thickness of material, concentration of syrup and
temperature on water loss and solid gain. At the end of every 2, 1
and 0.5 h at RT, 50 and 75 oC, respectively, the slices were blotted
out to remove the syrup adhering to it and weighted. Sample of
5 g were taken from each treatment and kept in the oven for the
determination of moisture content and solid gain. The water loss
and solid gain in the osmotic process were calculated using the
following formula: Weight reduction (WR) in (%) = ((Initial fruit
weight - final weight)/ (Initial fruit weight)) x 100. Solid gain
(SG) = ((Total solids-Initial solids) / (Initial fruit weight)) x 100.
Water loss = WR+SG.
reached constant weight. Similar to air drying, the slices were
taken out and weighed at every 1 h time interval. The air and
vacuum dried fruits were allowed to reach room temperature and
packed in polyethene bags of 100 mm thickness. The experiment
was replicated thrice and average values were obtained. For the
determination of moisture content, 5 g of sample was dried in
a vacuum drier at 70 oC and 660 mm of vacuum till it attained
constant weight. The data were subjected to statistical analysis
as outlined by (Panse and Sukhatme, 1964). Wherever possible
the statistical significance was tested by ‘F’ values at 5 percent
level of probability and the critical differences were worked out
for the significant effects
After osmosis, the slices were taken out from the syrup and blotted
completely with a tissue paper to remove the syrup adhered in the
pieces. The slices were then weighed and either dried or directly
packed in 100 mm thick polyethene bags as intermediate moisture
food. The slices were spread uniformly on aluminum trays in a
single layer and dried in a cabinet dryer at 65 oC until constant
weight was reached. In the dryer, the hot air temperature could be
adjusted thermostatically from RT to 250 oC. The weight of the
slices was recorded at every 1 h time interval. In case of control,
the fresh slices were directly dehydrated in the cabinet dryer.
Results and discussion
In vacuum drying, the slices were dried in a vacuum oven at 70
o
C and 600 mm of vacuum. Drying was continued till the slices
The results obtained revealed that water loss in banana slices
was significantly influenced by osmosis time, thickness of slices,
concentration of sugar syrup and temperature. The interaction
effect of thickness, concentration and temperature also favored
water loss significantly. During the period of osmosis the water
loss increased with increase in osmosis time while the rate of water
loss decreased, at all the temperature levels. It was observed that
more than 50 per cent of the dewatering occurred within the 4th,
2nd and 1st hrs of osmosis at RT, 50 and 75 oC, respectively. The
time required for maximum dewatering reduced by half to one
fourth at higher temperature (Table 1 & 2).
Table 1. Water loss (per cent) during osmosis in Poovan and Dwarf Cavendish at different interval
Syrup
Poovan
Thickness Osmosis
(mm)
temperature concentration
1
2
3
4
5
1
(oB)
(oC)
5
RT
40
10.93
19.06
23.70
28.20
31.36
13.10
50
12.90
22.00
28.53
33.93
38.40
17.06
60
15.00
26.30
34.73
41.06
44.70
19.70
50
40
12.83
21.86
28.60
33.80
36.36
14.30
50
17.40
29.00
37.03
43.50
46.03
18.53
60
18.36
32.03
41.96
48.23
52.02
21.70
75
40
16.00
26.00
32.80
37.60
40.70
14.96
50
18.26
31.10
40.63
47.10
49.70
17.56
60
18.53
33.10
42.63
48.43
53.10
20.00
7.5
RT
40
9.93
17.43
22.73
26.03
28.33
11.22
50
11.50
19.56
25.46
30.36
33.26
14.86
60
13.60
23.16
29.53
35.36
39.66
17.33
50
40
11.76
20.66
26.27
29.83
32.50
12.56
50
13.00
21.46
28.90
32.46
35.40
15.33
60
14.03
23.93
31.26
36.70
41.10
18.53
75
40
13.13
22.66
28.83
33.56
35.23
13.56
50
15.23
26.03
33.56
38.76
40.90
16.00
60
16.96
27.93
35.50
40.46
43.00
18.60
10
RT
40
8.76
15.40
19.93
22.70
24.70
9.80
50
10.96
19.40
24.40
27.80
31.13
11.90
60
12.80
21.76
28.46
34.00
37.90
14.60
50
40
10.70
18.46
23.36
27.23
39.53
11.13
50
12.83
21.70
26.96
31.13
34.06
14.36
60
14.03
24.33
30.96
35.30
38.43
16.76
75
40
12.83
19.36
25.10
29.20
31.36
12.60
50
14.93
24.86
31.90
36.60
39.53
15.00
60
16.66
27.13
33.90
38.86
42.06
17.26
Dwarf Cavendish
2
3
4
5
22.23
28.70
32.40
23.93
13.70
35.73
26.40
30.50
35.70
20.26
24.86
29.26
22.13
25.30
30.93
23.40
27.00
31.33
16.46
19.86
25.43
19.26
24.36
27.90
20.26
24.90
28.73
29.23
36.46
42.73
31.40
39.40
44.53
35.26
41.10
46.33
25.53
31.13
37.30
27.80
33.60
41.56
29.33
34.36
14.63
21.36
25.30
32.03
24.53
31.20
36.06
25.63
32.10
36.30
39.83
43.36
49.00
37.30
55.10
51.53
40.53
47.46
52.96
29.20
35.66
42.76
31.96
38.83
47.63
33.88
40.26
47.80
24.30
28.66
37.10
28.33
35.90
41.23
30.03
36.50
41.16
31.36
47.43
52.93
41.70
49.16
54.63
44.66
50.90
57.90
32.16
38.66
46.36
34.66
41.93
49.66
36.06
42.06
50.60
26.43
32.30
39.53
30.60
38.83
43.73
31.93
38.86
44.26
Studies on osmotic dehydration of banana cv. Poovan and Dwarf Cavendish
Table 2. Solid gain (per cent) during osmosis in Poovan and Dwarf Cavendish at differnt intervals
Syrup
Poovan
Thickness Osmosis
(mm)
temperature concentration
1
2
3
4
5
1
(oB)
(oC)
5
RT
40
2.03
3.40
4.13
4.86
5.23
2.63
50
75
7.5
RT
50
75
10
RT
50
75
143
Dwarf Cavendish
2
3
4
5
4.53
5.76
6.76
7.56
50
2.46
4.16
5.10
5.66
6.10
2.70
5.10
6.50
7.30
8.16
60
2.63
4.70
6.10
7.00
7.43
3.03
5.03
6.76
7.76
8.56
40
2.46
4.26
5.30
6.06
6.60
3.33
5.63
7.23
8.56
9.33
50
3.03
5.40
6.73
7.66
8.53
3.50
6.16
7.96
8.96
9.66
60
3.26
5.80
7.33
8.46
9.36
3.93
6.60
8.43
9.56
10.50
40
3.93
6.60
8.43
9.56
10.50
4.83
8.96
11.83
13.26
13.93
50
4.76
7.56
9.66
10.73
11.36
5.43
9.36
12.46
13.90
14.43
60
5.10
7.53
9.50
10.90
11.80
5.96
10.13
13.16
14.53
15.50
40
1.73
3.00
3.63
4.13
4.66
2.46
4.23
5.33
6.20
6.63
50
2.23
3.50
4.43
5.26
11.36
2.53
4.53
5.50
6.23
7.16
60
2.46
4.26
5.20
5.83
11.80
2.76
5.00
6.33
7.16
7.63
40
2.50
4.36
5.50
6.20
6.86
3.10
5.33
6.70
7.66
8.43
50
2.86
4.73
5.80
6.70
7.56
3.26
5.46
7.16
8.40
9.13
60
3.10
5.33
6.70
7.66
8.43
3.63
6.40
8.30
9.10
9.66
40
3.63
6.40
8.30
9.10
9.66
4.20
6.93
8.63
9.70
10.53
50
4.16
6.90
8.63
9.70
10.53
4.73
7.56
9.66
10.73
11.36
60
4.80
7.60
9.23
10.60
11.50
5.10
7.83
9.86
11.46
12.26
40
1.53
2.63
3.36
3.83
4.16
2.16
3.63
4.73
5.30
5.80
50
2.16
3.36
4.16
4.76
5.80
2.43
3.93
4.96
5.70
6.36
60
2.46
3.96
4.96
5.70
6.43
2.63
4.50
5.70
6.40
6.86
40
2.43
4.20
4.96
5.70
6.23
2.80
4.90
5.86
6.80
7.33
50
2.80
4.70
5.83
6.90
7.46
3.10
5.33
6.90
8.06
9.06
60
3.03
5.23
6.70
7.60
8.36
3.46
5.96
7.90
8.76
9.60
40
3.46
5.70
7.50
8.36
8.90
3.83
6.63
8.26
9.16
9.90
50
3.93
6.60
8.43
9.60
10.30
4.26
6.93
8.86
9.96
10.50
60
4.63
7.73
9.63
10.73
11.46
4.73
7.60
9.16
10.36
11.26
The water loss was higher in both rate and extent at 50 and 75 oC
when compared to RT in all syrup concentrations. The increase
in rate and extent of dewatering at high temperature might be
due to the changes in semi permeability of the cell membrane of
the fruit, allowing more water to diffuse out and rather in a short
period. This finding is in confirmation with the results obtained by
Ponting et al. (1966). Besides, at higher temperature, the viscosity
of the syrup decreased causing convention currents in the syrup,
which in turn eliminate local dilution and osmosis.
It was observed that the water loss increased with increase in
syrup concentration. The maximum water loss was found to
occur in slices treated with 60 oB syrup, at all the temperatures.
This might be due to the increased osmotic pressure in the sugar
syrup at higher concentration, which increased the driving force
available for water transport (Table 1). The increase in water loss
might be due to the increase in the surface area available for mass
transfer to take place when the slice thickness decreased. The
analysis showed the significant influence of time, concentration,
temperature and thickness on solid gain. The interaction of time,
temperature, concentration and thickness was also found to have
significant influence on the water loss.
From the Table 1, it is evident that the highest and lowest water
losses obtained for Dwarf Cavendish were 57.9 and 26.43 per
cent, respectively. It was approximately 2 to 4 per cent higher
compared to Poovan (AAB) and the effect was higher at elevated
temperature. The higher water loss realized in Dwarf Cavendish
(AAA) might be because of the higher initial moisture content
than Poovan (AAB). The water loss increased with increase in
osmosis time, temperature, and concentration in Poovan (AAB).
However, the increased in water loss with respect to thickness
was marginal.
Similar to water loss, the rate of solid uptake was higher during
the initial stages of osmosis. This is in agreement with the results
obtained by Conway et al. (1983) for apples. Changes in solid
gain might be because of the higher concentration difference
between solids in fruits and syrup at higher syrup concentrations.
Besides, temperature also influenced solid gain. Collapse of the
144
Studies on osmotic dehydration of banana cv. Poovan and Dwarf Cavendish
cell membrane resulted at 75oC. The semi permeable nature of
the membrane was affected which allowed more amount of solids
to get penetrated into the fruit. Similar to Poovan (AAB), the
solute gain in Dwarf Cavendish (AAA) increased with increase in
osmosis time, temperature and concentration. Unlike water loss,
the solute gain in Dwarf Cavendish (AAA) was influenced by
the thickness and had inverse relationship. It could be observed
that the water loss and gain were higher for Dwarf Cavendish
(AAA) than Poovan (AAB) (Table 2). This might be due to the
lower initial total soluble solids content of Dwarf Cavendish,
and was in agreement with the results obtained by Dalla-Rosa
et al. (1982).
The optimum values for maximum water loss with minimum solid
intake for Poovan (AAB) and Dwarf Cavendish (AAA) were at
slice thickness of 5 mm and osmosis in 60 oBrix sugar syrup at
50 oC for 5 h. Similar results were obtained by Bongirwar and
Sreenivasan (1977). The moisture content of the slices decreased
during osmosis. The moisture content in 5 mm thick Poovan and
Dwarf Cavendish was reduced to as low as 0.310 and 0.383 kg
H2O kg-1 DM from an initial value of 2.03 and 2.84 kg H2O kg-1
DM, respectively. Maximum moisture reduction occurred in
slices with minimum thickness and treated at higher temperatures
(Table 3).
Studies conducted on osmotic dehydration of banana using
sugar syrup revealed that the moisture loss and solid gain during
osmotic dehydration of banana slices are influenced positively by
the temperature and concentration of sugar syrup. The maximum
water loss was found to occur in slices treated with 60oB syrup,
at all the temperatures. The results also suggest that for bananas
osmotic dehydration, temperature is an important variable. Due
to the soft texture of bananas, osmotic treatment of bananas
needs not to be done at extreme conditions of temperature and
concentration. Results also suggest that a product for further
drying could be obtained by treating the slices at temperatures not
more than 50 oC and using osmotic syrup at 60 oBrix for 5 h.
Table 3. Moisture content (kg H2O kg-1 DM) in Dwarf Cavendish during osmosis at different interval
Thickness Osmosis
Syrup
Poovan
(mm)
temperature concentration
1
2
3
4
5
1
(oC)
(oB)
5
RT
40
1.599
1.317
1.166
1.025
0.932
2.216
50
75
7.5
RT
50
75
10
RT
50
75
Dwarf Cavendish
2
3
4
5
1.693
1.410
1.189
1.018
50
1.525
1.210
1.010
0.855
0.731
1.984
1.456
1.179
0.920
0.777
60
1.459
1.079
0.825
0.648
0.551
1.869
1.329
0.954
0.740
0.609
40
1.527
1.211
1.002
0.850
0.774
2.035
1.583
1.282
1.064
0.914
50
1.376
0.489
0.761
0.577
0.505
1.880
1.346
1.019
0.827
0.697
60
1.341
0.900
0.621
0.455
0.350
1.741
1.174
0.856
0.632
0.531
40
1.380
1.035
0.825
0.691
0.605
1.913
1.361
1.024
0.852
0.726
50
1.291
0.855
0.618
0.455
0.390
1.769
1.230
0.848
0.660
0.571
60
1.272
0.836
0.573
0.423
0.310
1.706
1.060
0.706
0.519
0.383
40
1.643
1.377
1.208
1.103
1.026
2.205
1.777
1.547
1.392
1.282
50
1.575
1.300
1.110
0.958
0.870
2.073
1.610
1.361
1.190
1.066
60
1.504
1.178
0.981
0.815
0.694
1.970
1.443
1.135
0.942
0.814
40
1.556
1.240
1.058
0.948
0.865
2.111
1.655
1.414
1.250
1.142
50
1.500
1.207
0.979
0.870
0.789
2.005
1.551
1.218
1.022
0.904
60
1.467
1.123
0.900
0.745
0.625
1.882
1.330
0.946
0.751
0.682
40
1.470
1.125
0.924
0.794
0.745
2.001
1.536
1.290
1.126
1.038
50
1.381
0.998
0.772
0.629
0.581
1.890
1.400
1.122
0.919
0.855
60
1.313
0.944
0.746
0.609
0.541
1.782
1.261
0.931
0.700
0.613
40
1.687
1.448
1.294
1.203
1.131
2.280
1.940
1.713
1.587
1.496
50
1.594
1.309
1.144
1.038
0.924
2.183
1.808
1.573
1.444
1.288
60
1.528
1.224
1.015
0.853
0.738
2.073
1.504
1.321
1.139
1.049
40
1.589
1.305
1.150
1.028
0.955
2.183
1.772
1.552
1.392
1.301
50
1.513
1.197
1.031
0.899
0.814
2.049
1.586
1.330
1.118
1.006
60
1.475
1.160
0.908
0.781
0.691
1.943
1.442
1.119
0.931
0.850
40
1.485
1.231
1.035
0.914
0.850
2.057
1.647
1.411
1.240
1.172
50
1.421
1.096
0.883
0.758
0.655
1.950
1.490
1.202
1.041
0.963
60
1.338
0.979
0.776
0.643
0.574
1.850
1.347
1.072
0.903
0.798
Studies on osmotic dehydration of banana cv. Poovan and Dwarf Cavendish
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Received: November, 2013; Revised: March, 2014; Accepted: March, 2014